1. Field of the Invention
The invention relates to a steering system and a tooth member used for the steering system.
2. Description of the Related Art
In a steering column apparatus described in Japanese Patent Application Publication No. 2007-238012 (JP 2007-238012 A), a steering shaft that couples a steering wheel and a steering mechanism together is inserted through a column body. To a side portion of the column body, a plate-like telescopic gear base is fixed which has a plurality of teeth formed on each of opposite sides thereof. The column body is provided with slots extending in a telescoping direction and through which a shaft with an operation lever attached thereto is inserted. A telescopic gear member is fixed to the operation lever in association with the telescopic gear base. The telescopic gear member has, on a surface thereof that faces the teeth of the telescopic gear base, a plurality of teeth arranged at the same pitch as the teeth of the telescopic gear base are arranged. Pivoting the operation lever causes the telescopic gear member to mesh with the telescopic gear base. Consequently, telescopic position adjustment for the column body is restricted.
In the steering system described in JP 2007-238012 A, the teeth of the telescopic gear member are meshed with teeth of a tooth member with the teeth formed on opposite surfaces thereof such as the telescopic gear base in order to restrict extension and contraction of a column jacket such as the column body after the telescopic position adjustment is performed. Portions of the tooth member in which tops of the teeth are formed are different in thickness from portions of the tooth member in which roots of the teeth are formed. Thus, for example, when a tooth member is formed by compression molding, the portions of the tooth member in which the tops of the teeth are formed are different from the portions of the tooth member in which the roots of the teeth are formed in compressibility in compression molding, in other words, density. Therefore, mechanical performance such as the strength of the tooth member in a direction in which the teeth are arranged may be unstable, in turn making the strength of meshing between the tooth member and the telescopic gear base unstable.